Process for producing a homogeneous low softening point, optically anisotropic pitch

Abstract

A process for producing optically anisotropic pitch containing 80% or more of an anisotropic phase. A starting material is pyrolytically polycondensed. Afterward, the material is maintained at a temperature of between 350 DEG and 400 DEG C. to precipitate a portion of the material rich in the anisotropic phase having a high specific gravity. This portion is separated and further heat treated.

What is claimed is: 
     
       1. A homogeneous, low softening point, optically anisotropic pitch containing approximately 80% or more of an optically anisotropic phase and a softening point of approximately 320° C. or below, said pitch prepared by: (1) providing a pitch-like material comprising a mixture of compounds consisting of carbon and hydrogen and having an approximate boiling point of 540° C. or higher, said mixture being substantially free from quinoline insolubles, said mixture containing a first component soluble in n-heptane and a second component insoluble in n-heptane and soluble in benzene, each aromatic carbon fraction of such components being about 0.7 or higher, each number average molecular weight being about 1,500 or less, and each maximum molecular weight being approximately 10,000 or less;   (2) heating said pitch-like material at temperatures in the range of from about 380° C. to about 440° C. for a time sufficient to form about 20% to about 70% of an optically anisotropic phase;   (3) maintaining said heated pitch-like material at temperatures in the range of from about 350° C. to about 400° C. for a time sufficient for said heated pitch material to form an upper layer and a lower layer;   (4) separating said lower layer from said upper layer; and   (5) heating said lower layer at a temperature in the range of from about 380° C. to about 440° C. for a time sufficient to increase the optical anisotropic phase content of said separated lower layer to 80% or more.   
     
     
       2. The pitch-like material of claim 1, further including a third component insoluble in benzene and soluble in quinoline. 
     
     
       3. The pitch-like material of claim 2, wherein each aromatic carbon fraction of said first component, said second component and said third component is about 0.75 or higher. 
     
     
       4. The pitch-like material of claim 1, wherein each number average molecular weight of said first Component and said second Component is between 250 and 900, and each maximum molecular weight is 3,000 or less. 
     
     
       5. The pitch-like material of claim 3, wherein the aromatic carbon fraction of the third component is approximately 0.8 or higher, its number average molecular weight is approximately between 500 and 1,200 and its maximum molecular weight is approximately 5,000 or less. 
     
     
       6. The pitch of claim 1, wherein the softening point of said optically anisotropic pitch is in the approximate range of between 230° and 320° and the content of the optically anisotropic phase therein is in the approximate range of between 90 and 100%. 
     
     
       7. The pitch of claim 6, wherein said pitch-like material is heated under normal pressure while passing or bubbling inert gas and simultaneously removing low molecular weight substances. 
     
     
       8. The pitch of claim 6, wherein said pitch-like material is heated under normal pressure and thereafter low molecular weight substances are removed by distillation under reduced pressure or inert gas stripping treatment. 
     
     
       9. The pitch of claim 6, wherein said pitch-like material is heated under elevated pressure and thereafter distillating under reduced pressure or stripping treatment with an inert gas. 
     
     
       10. The pitch of claim 6, wherein said pitch-like material is heated while simultaneously separating the optically anisotrpic phase being formed. 
     
     
       11. A process for producing a homogeneous, low softening point, optically anisotropic pitch containing approximately 80% or more of an optically anisotropic phase and a softening point of approximately 320° C. or below, comprising the steps of: (a) pyrolytically polycondensing a pitch-like material which is a mixture comprising compounds consisting of carbon and hydrogen and having a boiling point of approximately 540° C. or higher and is substantially free from quinoline insolubles, said pitch-like material containing a first Component soluble in n-heptane, and a second Component insoluble in n-haptane and soluble in benzene, an aromatic carbon fraction of each component being approximately 0.7 or higher, each number average molecular weight being approximately 1,500 or less, and each maximum molecular weight being approximately 10,000 or less, said pyrolytically polycondensing said pitch-like material being achieved by heating the said pitch-like material at a temperature in the range of about 380° C. to 440° C. until the content of pyrolytically polycondensed pitch-like material has an optically anisotropic phase of between approximately 20 and 70%, (b) thereafter maintaining said pitch-like material at a temperature in the approximate range of between 350° and 400° C. to form an upper layer and a lower layer, said lower layer being rich in the optically anisotropic phase; (c) separating the lower layer; and (d) heating said separated lower layer at temperatures in the range of about 380° C. to about 400° C. for a time sufficient to increase the optically anisotropic phase of said lower layer to greater than about 80%. 
     
     
       12. The process of claim 11, wherein the pitch-like-material further comprises a third component insoluble in benzene and soluble in quinoline. 
     
     
       13. The process of claim 11, wherein each aromatic carbon fraction of said components is approximately 0.75 or higher. 
     
     
       14. The process of claim 12, wherein each number average molecular weight of said first Component and said third Component is approximately between 250 and 900 and each maximum moleculr weight is approximately 3,000 or less. 
     
     
       15. The process of claim 11, wherein the aromatic carbon fraction of said second Component is approximately 0.8 or higher, its number average molecular weight is approximately between 500 and 1,200 and its maximum molecular weight is approximately 5,000 or less.